LabVIEW programming

Good Morning

Has anyone had experience using or programming in LAbVIEW.

I am trying to build an elapsed timer to track cycle duration. so far I found 10 way NOT to track time.

any help would be appretiated

LabVIEW full development systems. Embedded Microsoft touch screen. Eight slot rack, two AC inputs Two temp inputs and a 4-20 card (close loop)

Thanks for your time and attention.

Hi John,

Yeah I have played around a little bit with Labview, even got my CLAD .

What version are you using?
What time range are you looking at? (1-2 ms or several seconds)

Yes, but mostly long ago w/ LabView 5. It is much improved since. Most engineers were exposed to it in school, especially EE and it has long been popular in Physics mainly due to its MacIntosh heritage. If your timer is long duration so that the non-realtime aspect of Windows is acceptable (about +/-0.3 sec), then regular LabView should be fine. Otherwise, I think you need LabView RT and its associated hardware (FPGA boards) and the price of the software alone may shock you (~$8K last I was quoted).

Above assumes you are using the CPU for timing. Even in Windows, the absolute time should be accurate, it is just erratic in getting the value to your LabView program, i.e. the +/-0.3 sec error doesn't grow. So if just for human display it shouldn't matter. Another way to time accurately is to use an NI counter-timer board and have your program poll it for the current clock count. PC clocks are typically +/-30 ppm accurate. Counter-timer boards have their own clock which is likely more accurate.

Nothing really sensitive. The longest time would be 18 minutes. shortest would be ten minutes. Nothing down to millisecond. Nearest whole value will suffice.

version 15

I am trying to find a VI that will allow a trigger and a stable unit of measure relative to the duration, that I can change into a minute.

Just haven't found it among the trillion or so VI functions in this Version.

I was on the verge of using a tick timer, an and gate, and a count register, haven't found the right count register yet.

It's like setting out to find the holy grail. You know it's out there just not sure where to look.

Have used it extensively. Am a Certified Developer. You would have better luck at the NI site. I use a functional global for tracking time. One state sets the start time, then another state reads current time and subtracts the stored time from current time to give elapsed time. There is a canned elapsed time function, but I never used it. There is a danger of the PC time rolling over and messing up the time. That happens about once a month.

Ooh I've tried NI

Posted discussions, waiting on an engineers to get back with me on the time tracking issue...............for three days.

There is so much talent here I though i might have some luck.

I am reading Global Variables now, thanks for the tip

I put together a quick example. I would normally have one state of my state machine load the start time, then another state would query it.
https://www.dropbox.com/s/gwigptgutimqwbx/Elapsed Time Example.zip?dl=0

Thank you Highland

Much appreciated.

I will look these over.

Here is my very simple method for a timer in LabVIEW 2013

https://www.youtube.com/watch?v=iQWO7i4ZVUw

That's so much easier then the way I have been trying

I need to ask, can this be triggered off a 120 volt input, monitor, and be reset when the signal goes away. I also need to Log the final number in a spread sheet.

Is there a VI that converts seconds to minutes, cause I havent found one yet, in LabVIEW's warehouse of pallets.

Thank you for this wonderfully easy Idea.

Can I ask again, in your opinion, I have one while loop around six tanks. but not all tanks start at the same time. If I put a while loop around each tank and trigger with a 120 volt input, how can I log each element ( time, temp, conductivity) on each tank, on the same spread sheet. get a little foggy here.

I need to have a pop up screen with numeric key pad to input basket numbers to tank one, then need to increment that number to the next tank upon conclusion. I have been unable to locate a "Shift Register" in the VI pallets, nor a numeric input device.

Again you have been unbelievably helpful and I am very grateful.

Thank you

John Morris said:

I need to ask, can this be triggered off a 120 volt input, monitor, and be reset when the signal goes away. I also need to Log the final number in a spread sheet.

Click to expand...

Yes but define your hardware. You may need an interposing relay. The only voltages I have seen with LV are 5V and 24V.

Eight slot rack

Click to expand...

A PXI rack?

Is there a VI that converts seconds to minutes, cause I havent found one yet, in LabVIEW's warehouse of pallets.

Click to expand...

I can lookup example code for this, but I think it's simpler to change the 1000 constant in the ms to wait in my example to 60,000.

Can I ask again, in your opinion, I have one while loop around six tanks. but not all tanks start at the same time. If I put a while loop around each tank and trigger with a 120 volt input, how can I log each element ( time, temp, conductivity) on each tank, on the same spread sheet. get a little foggy here.

Click to expand...

I would need to have a play about with that, and I won't get time until the weekend.

I need to have a pop up screen with numeric key pad to input basket numbers to tank one, then need to increment that number to the next tank upon conclusion. I have been unable to locate a "Shift Register" in the VI pallets, nor a numeric input device.

Click to expand...

Numeric input is called "numeric control" found by right clicking the front panel (not block diagram), numeric tab, 2nd in. I don't think there is one that emulates a key pad as such, you could create your own I guess. (Right click a group of objects on front panel and select "Make type def").

Shift registers are handled at loop level, right click on the side of for loop and select "Add shift register".

One thing to be wary of, with while loops, always add a ms to wait timer within the while loop. I didn't do this in my sample code earlier ^

Set it to 1ms even, the reason is if you don't and you deploy to a machine with a low end CPU, the CPU will spend all it's time trying to execute the while loop as fast as possible. I have 16 threads on this machine, so not too worried lol.

I have two 120 v input cards. Actually the are 50 to 250 vac

Not sure what a PIX rack is, I have a c-DAQ 9178 eight slot rack, with six cards. Also using the NI embedded touch screen so processing isn't an issue.